Process of building an Airplane Engine monitor. It will connect a Arduino to an Android phone or Tablet.

Sunday, April 6, 2014

After You Rewire it...

Yesterday I stopped by an estate sale. They had a Robosapian V2 for $10. This is a robot I've wanted for years, but they cost more than I could justify. I thought $10, why not. The remote seemed to work, and it had batteries in it, I thought for $10, I would take a chance on it.

It needs 6D cells and 4AAA batteries, so I stopped off and picked up some batteries for another $15. So now I am $25 into it, and it doesn't seem to work. My normal mode after buying something like this, and finding it doesn't work, is I Google for similiar failure modes. This failure mode is, it does nothing. I opened up the feet again to be sure I put the batteries in the right way, which I have, but the one pair of AAA batteries are super hot, like I can't hold them.

Reading some of the fixes suggested, was a youtube video about how easy it is to rewire this thing. I watched about half of it, and thought, this is like Tim Taylor rewiring everything just because. Another site suggested rewiring the legs. The one site suggested it is easy to open the robot up, so I thought, I can open up the torso to measure voltages on the main board.

Insulation has flaked off and is covering bits of the robot insides.

What greeted me when I opened it up was shocking! Insulation just flaking off of the wires. Most of the wires that went to the legs had about 50% of the insulation missing. I continued opening up the robot, and when I got to the legs, there were parts where all I saw was a mass of copper, you could no longer tell one wire from another.

I thought I would try the rewiring repair. I went to Radio Shack to see what they had for wire. There was a significant gap between the 22GA wire and the 30GA wirewrap wire that they didn't have. I bought the 22GA wire to use for the motor power, and decided to cannibalize a Cat 5 cable for the logic wiring. It took about 4 hours to do all the wiring. There are several sites with details on what the wires are for.

I want to blame some MBA or manager for making a really bad choice here. I don't know for sure, but someone at the company decided to cut some corners with the quality of the wire. Some of the wire in the robot is fine, but the critical wires (the ones going from the body where the computer is, to the feet where the batteries are, and they move a lot) are just crap.

I was short of resources as well. The connectors that are in the robot are pretty cheap as well, but are a common connector. They have tin crimp on pins. Rather than risk the whole pin, or the body of the connector, I decided to strip back about an 1/8" of wire and solder my new wire on with some heat shrink to insulate the connection.

Once I got the wiring done, it still didn't work. I tried using a meter to trace the trouble. I was not getting any voltage from the AAA batteries in the one foot. When I opened that up, I found the connector in the cover was covered with corrosion, and not making good contact. After cleaning up the connection here, the robot started jiggling around and talking!

Success! I now had a working Robosapian V2. I started putting the panels back on, and covering the robot up, so it looked like it did when I brought it home. I messed up on some of the screw placement, but it went together, and looked good.

I played with the sensors for a little while last night. The blob detector is pretty good, and worked really well. The motion detector was pretty good at well, I could get it to flail backwards and scream when I swatted my hand towards the head. It walked and reached with the remote. So I went to bed.

When I got up this morning, I started messing with it more. I wasn't using the manual, just randomly pushing buttons. I clicked on the "D" button that starts the dance routine. It was playing music and moving quite a lot, then it quit. It seemed to quit on a proper down beat, but was in an odd position to end a dance.

3 of 6 wires are broken from white connector

Nothing worked again. Grrr! how much do I need to open up to find the trouble this time? I opened the torso, and the trouble was obvious. My soldering on to the connector ends made the wire brittle. People have told me before, "don't solder your crimp connectors, it makes the wire brittle", but in this case, I didn't have much choice. Most of the wire was already missing the insulation, and I didn't think making long pigtails with lots of heat shrink was a good idea. (I didn't think of long heat shrink coated wires at all).

I've ordered some new connectors. I will replace all 4 of the connectors I soldered to like that, and make sure there is enough jiggle room between the connector and the solder joint.